Pirating of digitally-formatted works have been a significant obstacle towards the widespread adoption and use of the Internet for distribution of media such as books, musical works, and motion pictures. Although such network distribution would at first glance seem ideal for these media, which are easily represented in electronic format, there has been no easy way to prevent widespread illegal copying of such works once they are introduced to the public. In many cases, a person will buy a legitimate copy and then distribute illegal copies thereof to friends and others without any further payments to the publisher. This threatens the financial well-being of the publishers, and makes them very reluctant to introduce their works through the Internet.
Therefore, in an attempt to solve the above described problems, digital watermarking has been developed. In general, digital watermarking is an alteration of a data set within an electronic file. The watermark can be visible or invisible to the naked human eye.
The invisible, or nearly invisible, watermark is mainly detected by a computer. The computer computes a correlation of the information under scrutiny with an applied watermark pattern, and compares the result of the correlation with a predetermined threshold. If the difference is greater than the threshold, the watermark is said to be present; otherwise, it is said to be absent. The greater the difference, the more reliable the detection. However, with respect to works embedded with such a watermark, a great deal of computing is needed to detect the watermark and identify copyright notices and/or other verification messages in these works. In addition, once these works are printed, it becomes more difficult to accurately read or interpret information contained in the watermark, due to the imperceptible characteristics of the watermark.
What is needed, therefore, is a digital watermarking system and method, which can efficiently watermark text information including background images and generate a perceptible watermark.